The present invention relates to an intraocular lens implant.
The crystalline lens is a transparent structure that focuses light in the human eye. Opacification of the lens known as cataract formation is a common cause of poor vision in the elderly, and can be corrected surgically.
Modern cataract surgery is performed by manual extracapsular cataract extraction, or by phacoemulsification. Manual extracapsular cataract extraction involves expressing the hard nucleus of the cataract through a 10 mm to 12 mm incision. Phacoemulsification utilises ultrasonic energy transmitted by a needle to fragment the nucleus and allow aspiration of the cataract through a 2.8 mm to 3.2 mm incision. In both operations an opening is made in the anterior capsule to allow removal of the lens contents. The capsular bag remnant, however, is left in situ to provide support for an intraocular lens implant which is inserted following removal of the cataract to replace the focussing power of the natural crystalline lens.
It is known to provide an intraocular lens implant which typically comprises a central focusing element, known as the optic, and a peripheral support structure, known as the haptic. The optic and the haptic of the intraocular lens may be manufactured from transparent rigid plastics material such as polymethyl methacrylate, or from flexible plastics material such as silicone or hydrogel. Intraocular lens implants manufactured from flexible material are preferable to those made of rigid material because the lens may be folded to allow insertion through a small incision in the sclera or outercoat of the eye and is then required to unfold to its original dimension.
The optic and haptic of the intraocular lens may be manufactured from the same material as a single piece unit or the haptic may be attached to the optic by a variety of mechanisms. There may be one or a plurality of haptics attached to the optic, although the most common configuration includes an optic with two outwardly extending haptics. The purpose of the haptic is to provide optimal centration of the optic as well as a means of fixation of the implant within a capsular bag remnant of the original lens following cataract or lens extraction. It is preferable that the haptics conform to the periphery of the capsular bag to provide a larger surface area of contact between the intraocular lens implant and the capsular bag and to ensure centration of the optic. It is also possible to implant a lens in front of the anterior capsule behind the iris with the haptics resting in the region between the root of the iris and cilairy processes, known as the cilairy sulcus. Intraocular lenses may also be inserted in phakic eyes to correct refractive errors, such as myopia or hyperopia, in front of the crystalline lens behind the iris with the haptic providing support in the cilairy sulcus. Furthermore, as an alternative site of implantation in phakic eyes, intraocular lenses may be inserted in front of the iris in the anterior chamber with the haptics resting in the angle of the anterior chamber.
In all these instances it is preferable that the haptics conform to the periphery of the capsular bag or to the cilairy sulcus, phakic eye or the angle of the anterior chamber. The prior art discloses several haptic designs, including a flange style or loop style, which seek to maximise the surface area of contact between the intraocular lens implant and the capsular bag. The most common design includes two loop style haptics attached at diametrically opposed points of an optic wherein terminal ends of the haptics extend arcuately towards the periphery of the capsular bag.
The fixation and stability of the intraocular lens implant is not solely dependent on the rigidity of the supporting haptics of an intraocular lens, but is also dependent on fusion of leaflets of anterior and posterior capsule in the interval between the optic of the implant and the terminal of the haptic in contact with the periphery of the capsular bag. It is preferable to maintain as large an interval as possible to provide maximum opportunity for fusion to occur.
Post-operative shrinkage of the capsular bag is not an unusual occurrence. The aforementioned interval may be maintained by a rigid haptic which resists shrinkage of the capsular bag, or by a design for haptics manufactured from flexible plastics which maintains an interval between the terminal of the haptic and the optic in the event of shrinkage of the capsular bag. In order that the design should accommodate the various sizes of capsular bag that will be encountered in different individuals as well as the varying degrees of shrinkage that would occur during the post-operative phase, it is preferable that the haptics should be compressible.
A distinct disadvantage, however, of the current haptic designs is that the haptic terminal may be flexed at any point between the haptic terminal and the haptic optic junction towards the optic such that the interval between the haptic terminal and the optic is reduced to the extent where migratory fusion of the leaflets of the anterior and posterior capsule fails to occur.
The present invention seeks to overcome the aforementioned disadvantages and provide better conformity of the terminal of the haptic with the periphery of the capsular bag, or to the cilairy sulcus, or to the angle of the anterior chamber. Since the greatest proportion of the intraocular lens implants are made with respect to a capsular bag remnant it is preferable that a haptic design should allow the terminal of the haptic to conform to the periphery of the capsular bag.
In accordance with one aspect of the invention there is provided an intraocular lens implant including an optic and a haptic, the haptic including a first portion extending outwardly in a first direction from the optic, a second portion which has an outermost end, extending outwardly in a second opposing direction to the first portion, and a bend member intermediate the first portion and the second portion, the bend member interconnecting the first portion and second portion, an end of the first portion remote from the bend member being connected to the optic at a haptic optic junction and the outermost end of the second portion being located on a side of the haptic optic junction opposite to the side on which the bend member is located.